<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        //括号里面是形参 可以有好多个
        function num(m) {
            var num = 0
            for (i = 0; i <= m; i++) {
                num += i
            }
            alert(num)
        }
        //调用函数 调用几次执行几次
        num(100) //括号里是实参 第一个数对应第一个形参
        num(1000)
    </script>
</body>

</html>